1. Field of the Invention
This invention relates to an improvement on a caliper guiding mechanism employed in a pin-slide type disc brake.
2. Description of the Prior Art
In a disc brake of this type, as disclosed by a U.S. Pat. No. 4,042,074 for example, a claiper which has a pair of confronting parts disposed on both sides of a disc is arranged to push one of the friction pads which are also disposed on both sides of the disc against one side of the disc by means of a hydraulic pressure operating mechanism disposed within one of the confronting parts of the caliper; then, the other of the confronting parts of the caliper is slided in the axial direction of the disc by a reaction to the pushing action; and then this sliding movement pushes the other friction pad disposed on the other side of the disc against this side of the disc. This sliding movement of the caliper is effected by a caliper guiding mechanism which comprises a pair of slide pins arranged in parallel with each other and interposed in between the caliper and a fixed support member disposed at the periphery of the disc.
The caliper guiding mechanism is arranged such that each slide pin is fixedly secured either to a support member or to a caliper member and the sliding movement of the caliper member is guided by sliding engagement of each of the slide pins with an opening provided either in the support member or in the caliper member. Generally, however, the sliding engagement of one slide pin is arranged in a different manner from that of the other slide pin according to their positions relative to the rotating direction of the disc. In other words, the slide pin which is located on the incoming side of the disc rotation during the forward movement of a vehicle is arranged to be in metallic contact with the above stated opening, because it receives a portion of a braking torque during brake application and also for the purpose of ensuring that the caliper slides in the correct direction. On the other hand, the slide pin which is located on the outgoing side of the disc rotation is arranged to be in auxiliary sliding contact with the above stated opening through an elastic matter such as a rubber bush that permits a certain degree of a relative movement in the radial direction to absorb deviation from a given distance between the pair of slide pins resulting from a machining error or a change in the parallel positions of these pins caused by a braking torque during brake application.
In the caliper guiding mechanism of the disc brake of the type having one of such slide pins (hereinafter will be called the main slide pin) arranged to be in metallic sliding contact and the other slide pin (hereinafter will be called the auxiliary slide pin) arranged to be in auxiliary sliding contact through an elastic bush, the difference between these slide pins in sliding resistance tends to cause uneven wear and dragging of the friction pads. The present invention is directed to the prevention of such uneven wear and dragging of the friction pads.
With the auxiliary slide pin arranged to be in slidable engagement through an elastic matter while the main slide pin is in metallic contact engagement, the sliding resistance of one slide pin is sometimes about 10 times as much as that of the other slide pin. Therefore, it has been difficult to ensure smooth sliding of the caliper on such a pair of slide pins.